(v2.8) Objects disappearing from viewport when going from UV Editor to Texture Paint
This one took an obnoxious amount of time to figure out how to get it to reappear, and even then I'm unable to replicate the problem of getting it to disappear now. If I can replicate the problem, I'll update my question further.
All it took to get the item to reappear was to go into local view by pressing / on the numpad to get it to re-appear.
The / on the Numpad toggles Local View.

Local view isolates the selected object or objects, so that they are
the only ones visible in the viewport.Source: The official Blender Documentation version 2.92